From abec8df9e0cc725c5c2227b12f7c1db6f0f7d0b4 Mon Sep 17 00:00:00 2001
From: Lucas Bremgartner <lucas@bremis.ch>
Date: Thu, 7 Mar 2024 12:50:06 +0100
Subject: [PATCH] Add support for generic types expressed by selector
 expressions

---
 generator/generator.go     |   4 +-
 generator/generics.go      |  38 ++++++++----
 generator/generics_test.go | 116 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 144 insertions(+), 14 deletions(-)

diff --git a/generator/generator.go b/generator/generator.go
index afc0b6e..34e5e32 100644
--- a/generator/generator.go
+++ b/generator/generator.go
@@ -335,7 +335,7 @@ func findTarget(input processInput) (output processOutput, err error) {
 	}
 
 	output.imports = imports
-	output.genericTypes = buildGenericTypesFromSpec(ts)
+	output.genericTypes = buildGenericTypesFromSpec(ts, types, input.astPackage.Name)
 
 	if it, ok := ts.Type.(*ast.InterfaceType); ok {
 		output.methods, err = processInterface(it, targetProcessInput{
@@ -555,7 +555,7 @@ func processIdent(i *ast.Ident, input targetProcessInput) (methodsList, error) {
 				return nil, errors.Wrap(errNotAnInterface, t.Name.Name)
 			}
 
-			genericsTypes = buildGenericTypesFromSpec(t)
+			genericsTypes = buildGenericTypesFromSpec(t, input.types, input.typesPrefix)
 			break
 		}
 	}
diff --git a/generator/generics.go b/generator/generics.go
index bc163f9..780956a 100644
--- a/generator/generics.go
+++ b/generator/generics.go
@@ -77,22 +77,40 @@ func (g genericTypes) buildVars() (string, string) {
 	return buildGenericsWithBrackets(types), buildGenericsWithBrackets(params)
 }
 
-func buildGenericTypesFromSpec(ts *ast.TypeSpec) (types genericTypes) {
+func buildGenericTypesFromSpec(ts *ast.TypeSpec, allTypes []*ast.TypeSpec, typesPrefix string) (types genericTypes) {
 	if ts.TypeParams != nil {
 		for _, param := range ts.TypeParams.List {
 			if param != nil {
-				if gpt, ok := param.Type.(*ast.Ident); ok {
-					var paramNames []string
-					for _, name := range param.Names {
-						if name != nil {
-							paramNames = append(paramNames, name.Name)
+				var typeIdentifier string
+				switch t := param.Type.(type) {
+				case *ast.Ident:
+					prefix := ""
+					if typesPrefix != "" {
+						for _, at := range allTypes {
+							if at.Name.Name == t.Name {
+								prefix = typesPrefix + "."
+								break
+							}
 						}
 					}
-					types = append(types, genericType{
-						Type:  gpt.Name,
-						Names: paramNames,
-					})
+
+					typeIdentifier = prefix + t.Name
+				case *ast.SelectorExpr:
+					typeIdentifier = t.X.(*ast.Ident).Name + "." + t.Sel.Name
+				default:
+					panic("unsupported generic type")
+				}
+
+				var paramNames []string
+				for _, name := range param.Names {
+					if name != nil {
+						paramNames = append(paramNames, name.Name)
+					}
 				}
+				types = append(types, genericType{
+					Type:  typeIdentifier,
+					Names: paramNames,
+				})
 			}
 		}
 	}
diff --git a/generator/generics_test.go b/generator/generics_test.go
index e10c803..d985179 100644
--- a/generator/generics_test.go
+++ b/generator/generics_test.go
@@ -79,7 +79,9 @@ func Test_genericTypes_buildVars(t *testing.T) {
 
 func Test_buildGenericTypesFromSpec(t *testing.T) {
 	type args struct {
-		ts *ast.TypeSpec
+		ts          *ast.TypeSpec
+		allTypes    []*ast.TypeSpec
+		typesPrefix string
 	}
 	tests := []struct {
 		name      string
@@ -116,10 +118,120 @@ func Test_buildGenericTypesFromSpec(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "build generic types foo.Bar from spec",
+			args: args{
+				ts: &ast.TypeSpec{
+					TypeParams: &ast.FieldList{
+						List: []*ast.Field{
+							{
+								Type: &ast.SelectorExpr{
+									X: &ast.Ident{
+										Name: "foo",
+									},
+									Sel: &ast.Ident{
+										Name: "Bar",
+									},
+								},
+								Names: []*ast.Ident{
+									{
+										Name: "I",
+									},
+									{
+										Name: "O",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			wantTypes: genericTypes{
+				{
+					Type:  "foo.Bar",
+					Names: []string{"I", "O"},
+				},
+			},
+		},
+		{
+			name: "build generic types Bar from spec without types prefix",
+			args: args{
+				ts: &ast.TypeSpec{
+					TypeParams: &ast.FieldList{
+						List: []*ast.Field{
+							{
+								Type: &ast.Ident{
+									Name: "Bar",
+								},
+								Names: []*ast.Ident{
+									{
+										Name: "I",
+									},
+									{
+										Name: "O",
+									},
+								},
+							},
+						},
+					},
+				},
+				allTypes: []*ast.TypeSpec{
+					{
+						Name: &ast.Ident{
+							Name: "Bar",
+						},
+					},
+				},
+			},
+			wantTypes: genericTypes{
+				{
+					Type:  "Bar",
+					Names: []string{"I", "O"},
+				},
+			},
+		},
+		{
+			name: "build generic types Bar from spec with types prefix",
+			args: args{
+				ts: &ast.TypeSpec{
+					TypeParams: &ast.FieldList{
+						List: []*ast.Field{
+							{
+								Type: &ast.Ident{
+									Name: "Bar",
+								},
+								Names: []*ast.Ident{
+									{
+										Name: "I",
+									},
+									{
+										Name: "O",
+									},
+								},
+							},
+						},
+					},
+				},
+				allTypes: []*ast.TypeSpec{
+					{
+						Name: &ast.Ident{
+							Name: "Bar",
+						},
+					},
+				},
+				typesPrefix: "prefix",
+			},
+			wantTypes: genericTypes{
+				{
+					Type:  "prefix.Bar",
+					Names: []string{"I", "O"},
+				},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if gotTypes := buildGenericTypesFromSpec(tt.args.ts); !reflect.DeepEqual(gotTypes, tt.wantTypes) {
+			if gotTypes := buildGenericTypesFromSpec(tt.args.ts, tt.args.allTypes, tt.args.typesPrefix); !reflect.DeepEqual(gotTypes, tt.wantTypes) {
 				t.Errorf("buildGenericTypesFromSpec() = %v, want %v", gotTypes, tt.wantTypes)
 			}
 		})